Publications
116 results found
Kumar R, Mahajan S, Donaldson F, et al., 2024, Stability of Near-Surface Nitrogen Vacancy Centers Using Dielectric Surface Passivation., ACS Photonics, Vol: 11, Pages: 1244-1251, ISSN: 2330-4022
We study the photophysical stability of ensemble near-surface nitrogen vacancy (NV) centers in diamond under vacuum and air. The optically detected magnetic resonance contrast of the NV centers was measured following exposure to laser illumination, showing opposing trends in air compared to vacuum (increasing by up to 9% and dropping by up to 25%, respectively). Characterization using X-ray photoelectron spectroscopy (XPS) suggests a surface reconstruction: In air, atmospheric oxygen adsorption on a surface leads to an increase in NV- fraction, whereas in vacuum, net oxygen desorption increases the NV0 fraction. NV charge state switching is confirmed by photoluminescence spectroscopy. Deposition of ∼2 nm alumina (Al2O3) over the diamond surface was shown to stabilize the NV charge state under illumination in either environment, attributed to a more stable surface electronegativity. The use of an alumina coating on diamond is therefore a promising approach to improve the resilience of NV sensors.
Cowie BE, Mears KL, S'ari M, et al., 2024, Exploiting Organometallic Chemistry to Functionalize Small Cuprous Oxide Colloidal Nanocrystals., J Am Chem Soc, Vol: 146, Pages: 3816-3824
The ligand chemistry of colloidal semiconductor nanocrystals mediates their solubility, band gap, and surface facets. Here, selective organometallic chemistry is used to prepare small, colloidal cuprous oxide nanocrystals and to control their surface chemistry by decorating them with metal complexes. The strategy is demonstrated using small (3-6 nm) cuprous oxide (Cu2O) colloidal nanocrystals (NC), soluble in organic solvents. Organometallic complexes are coordinated by reacting the surface Cu-OH bonds with organometallic reagents, M(C6F5)2, M = Zn(II) and Co(II), at room temperature. These reactions do not disrupt the Cu2O crystallinity or nanoparticle size; rather, they allow for the selective coordination of a specific metal complex at the surface. Subsequently, the surface-coordinated organometallic complex is reacted with three different carboxylic acids to deliver Cu-O-Zn(O2CR') complexes. Selective nanocrystal surface functionalization is established using spectroscopy (IR, 19F NMR), thermal gravimetric analyses (TGA), transmission electron microscopy (TEM, EELS), and X-ray photoelectron spectroscopy (XPS). Photoluminescence efficiency increases dramatically upon organometallic surface functionalization relative to that of the parent Cu2O NC, with the effect being most pronounced for Zn(II) decoration. The nanocrystal surfaces are selectively functionalized by both organic ligands and well-defined organometallic complexes; this synthetic strategy may be applicable to many other metal oxides, hydroxides, and semiconductors. In the future, it should allow NC properties to be designed for applications including catalysis, sensing, electronics, and quantum technologies.
Kubitza N, Beckmann B, Jankovic S, et al., 2024, Exploring the Potential of Nitride and Carbonitride MAX Phases: Synthesis, Magnetic and Electrical Transport Properties of V<inf>2</inf>GeC, V<inf>2</inf>GeC<inf>0.5</inf>N<inf>0.5</inf>, and V<inf>2</inf>GeN, Chemistry of Materials, Vol: 36, Pages: 1375-1384, ISSN: 0897-4756
The chemical composition variety of MAX phases is rapidly evolving in many different directions, especially with the synthesis of carbides that contain two or more metals on the M-site of these layered solids. However, nitride and carbonitride MAX phases are still underrepresented, and only a few members have been reported that are for the most part barely characterized, particularly in terms of magnetic and electronic properties. Here, we demonstrate a simple and effective synthesis route, as well as a comprehensive characterization of three MAX phases, (i) V2GeC, (ii) the hitherto unknown carbonitride V2GeC0.5N0.5, and (iii) the almost unexplored nitride V2GeN. By combining a microwave-assisted precursor synthesis with conventional heat treatment and densification by spark plasma sintering, almost phase-pure (carbo)nitride products are obtained. Magnetic measurements reveal an antiferromagnetic-paramagnetic-like phase transition for all samples in the temperature range of 160-200 K. In addition, increasing the amount of nitrogen on the X-site of the MAX phase structure leads to a constant increase in the magnetic susceptibilities while the electrical resistivity is constantly decreasing. Overall, these findings provide crucial insights into how to tune the electronic and magnetic properties of MAX phases by only varying the chemical composition of the X-site. This further substantiates the demand for (carbo)nitride research with the potential to be extended to the remaining elemental sites within the MAX phase structure to push toward controlled material design and to achieve desired functional properties, such as ferromagnetism.
Kalha C, Ratcliff LE, Colombi G, et al., 2024, Revealing the Bonding Nature and Electronic Structure of Early-Transition-Metal Dihydrides, PRX Energy, Vol: 3
Basso M, Colusso E, Carraro C, et al., 2023, Rapid laser-induced low temperature crystallization of thermochromic VO2 sol-gel thin films, APPLIED SURFACE SCIENCE, Vol: 631, ISSN: 0169-4332
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- Citations: 1
Zhu Y, Vigil-Hernandez C, Kalha C, et al., 2023, Temperature-modulated solution-based synthesis of copper oxide nanostructures for glucose sensing, MATERIALS ADVANCES, Vol: 4, Pages: 3572-3582
Westhead O, Spry M, Bagger A, et al., 2023, The role of ion solvation in lithium mediated nitrogen reduction, Journal of Materials Chemistry A, Vol: 11, Pages: 12746-12758, ISSN: 2050-7488
Since its verification in 2019, there have been numerous high-profile papers reporting improved efficiency of lithium-mediated electrochemical nitrogen reduction to make ammonia. However, the literature lacks any coherent investigation systematically linking bulk electrolyte properties to electrochemical performance and Solid Electrolyte Interphase (SEI) properties. In this study, we discover that the salt concentration has a remarkable effect on electrolyte stability: at concentrations of 0.6 M LiClO4 and above the electrode potential is stable for at least 12 hours at an applied current density of −2 mA cm−2 at ambient temperature and pressure. Conversely, at the lower concentrations explored in prior studies, the potential required to maintain a given N2 reduction current increased by 8 V within a period of 1 hour under the same conditions. The behaviour is linked more coordination of the salt anion and cation with increasing salt concentration in the electrolyte observed via Raman spectroscopy. Time of flight secondary ion mass spectrometry and X-ray photoelectron spectroscopy reveal a more inorganic, and therefore more stable, SEI layer is formed with increasing salt concentration. A drop in faradaic efficiency for nitrogen reduction is seen at concentrations higher than 0.6 M LiClO4, which is attributed to a combination of a decrease in nitrogen solubility and diffusivity as well as increased SEI conductivity as measured by electrochemical impedance spectroscopy.
Snyder RM, Juelsholt M, Kalha C, et al., 2023, Detailed Analysis of the Synthesis and Structure of MAX Phase (Mo<sub>0.75</sub>V<sub>0.25</sub>)<sub>5</sub>AlC<sub>4</sub> and Its MXene Sibling (Mo<sub>0.75</sub>V<sub>0.25</sub>)<sub>5</sub>C<sub>4</sub>, ACS NANO, Vol: 17, Pages: 12693-12705, ISSN: 1936-0851
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- Citations: 1
Cowie BE, Häfele L, Phanopoulos A, et al., 2023, Matched ligands for small, stable colloidal nanoparticles of copper, cuprous oxide and cuprous sulfide, Chemistry: A European Journal, Vol: 29, Pages: 1-18, ISSN: 0947-6539
This work applies organometallic routes to copper(0/I) nanoparticles and describes how to match ligand chemistries with different material compositions. The syntheses involve reacting an organo-copper precursor, mesitylcopper(I) [CuMes]z (z=4, 5), at low temperatures and in organic solvents, with hydrogen, air or hydrogen sulfide to deliver Cu, Cu2 O or Cu2 S nanoparticles. Use of sub-stoichiometric quantities of protonated ligand (pro-ligand; 0.1-0.2 equivalents vs. [CuMes]z ) allows saturation of surface coordination sites but avoids excess pro-ligand contaminating the nanoparticle solutions. The pro-ligands are nonanoic acid (HO2 CR1 ), 2-[2-(2-methoxyethoxy)ethoxy]acetic acid (HO2 CR2 ) or di(thio)nonanoic acid, (HS2 CR1 ), and are matched to the metallic, oxide or sulfide nanoparticles. Ligand exchange reactions reveal that copper(0) nanoparticles may be coordinated by carboxylate or di(thio)carboxylate ligands, but Cu2 O is preferentially coordinated by carboxylate ligands and Cu2 S by di(thio)carboxylate ligands. This work highlights the opportunities for organometallic routes to well-defined nanoparticles and the need for appropriate ligand selection.
Morfill C, Pankratova S, Machado P, et al., 2023, Addition to "Nanostars carrying multifunctional neurotrophic dendrimers protect neurons in preclinical in vitro models of neurodegenerative disorders"., ACS Applied Materials and Interfaces, Vol: 15, Pages: 13824-13824, ISSN: 1944-8244
In the original version of this article (p. 47457), some acknowledgments were not included. In the revised Acknowledgments section provided below, we additionally provide The REC reference for the ethical approval of the human astrocyte isolation, an acknowledgment to Dr. Alize Proust at the Francis Crick Institute for establishing the triple coculture BBB model used in this study, and the reference and the grant number for the source of the human fetal material. This does not affect the results or conclusions of our work.
Furedi M, Fodor B, Marton A, et al., 2023, Internal wettability investigation of mesoporous silica materials by ellipsometric porosimetry, THIN SOLID FILMS, Vol: 768, ISSN: 0040-6090
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- Citations: 1
Jones LAH, Xing Z, Swallow JEN, et al., 2022, Band Alignments, Electronic Structure, and Core-Level Spectra of Bulk Molybdenum Dichalcogenides (MoS2, MoSe2, and MoTe2), JOURNAL OF PHYSICAL CHEMISTRY C, Vol: 126, Pages: 21022-21033, ISSN: 1932-7447
Fernando NK, Bostrom HLB, Murray CA, et al., 2022, Variability in X-ray induced effects in [Rh(COD)Cl]2 with changing experimental parameters, Physical Chemistry Chemical Physics, Vol: 24, Pages: 28444-28456, ISSN: 1463-9076
X-ray characterisation methods have undoubtedly enabled cutting-edge advances in all aspects of materials research. Despite the enormous breadth of information that can be extracted from these techniques, the challenge of radiation-induced sample change and damage remains prevalent. This is largely due to the emergence of modern, high-intensity X-ray source technologies and the growing potential to carry out more complex, longer duration in situ or in operando studies. The tunability of synchrotron beamlines enables the routine application of photon energy-dependent experiments. This work explores the structural stability of [Rh(COD)Cl]2, a widely used catalyst and precursor in the chemical industry, across a range of beamline parameters that target X-ray energies of 8 keV, 15 keV, 18 keV and 25 keV, on a powder X-ray diffraction synchrotron beamline at room temperature. Structural changes are discussed with respect to absorbed X-ray dose at each experimental setting associated with the respective photon energy. In addition, the X-ray radiation hardness of the catalyst is discussed, by utilising the diffraction data collected at the different energies to determine a dose limit, which is often considered in protein crystallography and typically overlooked in small molecule crystallography. This work not only gives fundamental insight into how damage manifests in this organometallic catalyst, but will encourage careful consideration of experimental X-ray parameters before conducting diffraction on similar radiation-sensitive organometallic materials.
Hariki A, Higashi K, Yamaguchi T, et al., 2022, Satellites in the Ti 1s core level spectra of SrTiO3 and TiO2, PHYSICAL REVIEW B, Vol: 106, ISSN: 2469-9950
Jackson AJ, Parrett BJ, Willis J, et al., 2022, Computational Prediction and Experimental Realization of Earth-Abundant Transparent Conducting Oxide Ga-Doped ZnSb2O6, ACS ENERGY LETTERS, Vol: 7, Pages: 3807-3816, ISSN: 2380-8195
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- Citations: 2
Morfill C, Pankratova S, Machado P, et al., 2022, Nanostars Carrying Multifunctional Neurotrophic Dendrimers Protect Neurons in Preclinical In Vitro Models of Neurodegenerative Disorders, ACS APPLIED MATERIALS & INTERFACES, Vol: 14, Pages: 47445-47460, ISSN: 1944-8244
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- Citations: 5
Fernando NK, Stella M, Dawson W, et al., 2022, Probing disorder in 2CzPN using core and valence states, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, Vol: 24, Pages: 23329-23339, ISSN: 1463-9076
Xu Z, Thakur PK, Lee T-L, et al., 2022, Complex Magnetic Order in Topochemically Reduced Rh(I)/Rh(III) LaM0.5Rh0.5O2.25 (M = Co, Ni) Phases, INORGANIC CHEMISTRY, Vol: 61, Pages: 15686-15692, ISSN: 0020-1669
Ratcliff LE, Oshima T, Nippert F, et al., 2022, Tackling Disorder in γ-Ga<sub>2</sub>O<sub>3</sub>, ADVANCED MATERIALS, Vol: 34, ISSN: 0935-9648
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- Citations: 3
Ratcliff LE, Oshima T, Nippert F, et al., 2022, Tackling Disorder in γ‐Ga<sub>2</sub>O<sub>3</sub>, Advanced Materials, Vol: 34, ISSN: 0935-9648
<jats:title>Abstract</jats:title><jats:p>Ga<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> and its polymorphs are attracting increasing attention. The rich structural space of polymorphic oxide systems such as Ga<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> offers potential for electronic structure engineering, which is of particular interest for a range of applications, such as power electronics. γ‐Ga<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> presents a particular challenge across synthesis, characterization, and theory due to its inherent disorder and resulting complex structure–electronic‐structure relationship. Here, density functional theory is used in combination with a machine‐learning approach to screen nearly one million potential structures, thereby developing a robust atomistic model of the γ‐phase. Theoretical results are compared with surface and bulk sensitive soft and hard X‐ray photoelectron spectroscopy, X‐ray absorption spectroscopy, spectroscopic ellipsometry, and photoluminescence excitation spectroscopy experiments representative of the occupied and unoccupied states of γ‐Ga<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub>. The first onset of strong absorption at room temperature is found at 5.1 eV from spectroscopic ellipsometry, which agrees well with the excitation maximum at 5.17 eV obtained by photoluminescence excitation spectroscopy, where the latter shifts to 5.33 eV at 5 K. This work presents a leap forward in the treatment of complex, disordered oxides and is a crucial step toward exploring how their electronic structure can be understood in terms of local coordination and overall structure.</jats:p>
Parvizian M, Balsa AD, Pokratath R, et al., 2022, The Chemistry of Cu<sub>3</sub>N and Cu<sub>3</sub>PdN Nanocrystals, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, Vol: 61, ISSN: 1433-7851
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- Citations: 8
Parvizian M, Duràn Balsa A, Pokratath R, et al., 2022, The Chemistry of Cu<sub>3</sub>N and Cu<sub>3</sub>PdN Nanocrystals**, Angewandte Chemie, Vol: 134, ISSN: 0044-8249
<jats:title>Abstract</jats:title><jats:p>The precursor conversion chemistry and surface chemistry of Cu<jats:sub>3</jats:sub>N and Cu<jats:sub>3</jats:sub>PdN nanocrystals are unknown or contested. Here, we first obtain phase‐pure, colloidally stable nanocubes. Second, we elucidate the pathway by which copper(II) nitrate and oleylamine form Cu<jats:sub>3</jats:sub>N. We find that oleylamine is both a reductant and a nitrogen source. Oleylamine is oxidized by nitrate to a primary aldimine, which reacts further with excess oleylamine to a secondary aldimine, eliminating ammonia. Ammonia reacts with Cu<jats:sup>I</jats:sup> to form Cu<jats:sub>3</jats:sub>N. Third, we investigated the surface chemistry and find a mixed ligand shell of aliphatic amines and carboxylates (formed in situ). While the carboxylates appear tightly bound, the amines are easily desorbed from the surface. Finally, we show that doping with palladium decreases the band gap and the material becomes semi‐metallic. These results bring insight into the chemistry of metal nitrides and might help the development of other metal nitride nanocrystals.</jats:p>
Kubitza N, Reitz A, Zieschang A-M, et al., 2022, From MAX Phase Carbides to Nitrides: Synthesis of V2GaC, V2GaN, and the Carbonitride V2GaC1-xNx, INORGANIC CHEMISTRY, Vol: 61, Pages: 10634-10641, ISSN: 0020-1669
McClelland I, El-Shinawi H, Booth SG, et al., 2022, The Role of the Reducible Dopant in Solid Electrolyte-Lithium Metal Interfaces, CHEMISTRY OF MATERIALS, Vol: 34, Pages: 5054-5064, ISSN: 0897-4756
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- Citations: 2
Xia Y, Ouyang M, Yufit V, et al., 2022, A cost-effective alkaline polysulfide-air redox flow battery enabled by a dual-membrane cell architecture, Nature Communications, Vol: 13, Pages: 1-13, ISSN: 2041-1723
With the rapid development of renewable energy harvesting technologies, there is a significant demand for long-duration energy storage technologies that can be deployed at grid scale. In this regard, polysulfide-air redox flow batteries demonstrated great potential. However, the crossover of polysulfide is one significant challenge. Here, we report a stable and cost-effective alkaline-based hybrid polysulfide-air redox flow battery where a dual-membrane-structured flow cell design mitigates the sulfur crossover issue. Moreover, combining manganese/carbon catalysed air electrodes with sulfidised Ni foam polysulfide electrodes, the redox flow battery achieves a maximum power density of 5.8 mW cm-2 at 50% state of charge and 55 °C. An average round-trip energy efficiency of 40% is also achieved over 80 cycles at 1 mA cm-2. Based on the performance reported, techno-economic analyses suggested that energy and power costs of about 2.5 US$/kWh and 1600 US$/kW, respectively, has be achieved for this type of alkaline polysulfide-air redox flow battery, with significant scope for further reduction.
Kalha C, Reisinger M, Thakur PK, et al., 2022, Evaluation of the thermal stability of TiW/Cu heterojunctions using a combined SXPS and HAXPES approach, JOURNAL OF APPLIED PHYSICS, Vol: 131, ISSN: 0021-8979
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- Citations: 1
Liu S, Ay A, Luo Q, et al., 2022, Oxidation of copper electrodes on flexible polyimide substrates for non-enzymatic glucose sensing, MATERIALS RESEARCH EXPRESS, Vol: 9
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Balliou A, Papadimitropoulos G, Regoutz A, et al., 2022, Low-Cost, High-Gain MoS<sub>2</sub> FETs from Amorphous Low-Mobility Film Precursors, ACS APPLIED ELECTRONIC MATERIALS, Vol: 4, Pages: 1175-1185
Kalha C, Ratcliff LE, Gutierrez Moreno JJ, et al., 2022, Lifetime effects and satellites in the photoelectron spectrum of tungsten metal, Physical Review B: Condensed Matter and Materials Physics, Vol: 105, Pages: 1-18, ISSN: 1098-0121
Tungsten (W) is an important and versatile transition metal and has a firm place at the heart of many technologies. A popular experimental technique for the characterization of tungsten and tungsten-based compounds is x-ray photoelectron spectroscopy (XPS), which enables the assessment of chemical states and electronic structure through the collection of core level and valence band spectra. However, in the case of tungsten metal, open questions remain regarding the origin, nature, and position of satellite features that are prominent in the photoelectron spectrum. These satellites are a fingerprint of the electronic structure of the material and have not been thoroughly investigated, at times leading to their misinterpretation. The present work combines high-resolution soft and hard x-ray photoelectron spectroscopy (SXPS and HAXPES) with reflected electron energy loss spectroscopy (REELS) and a multitiered ab initio theoretical approach, including density functional theory (DFT) and many-body perturbation theory (G0W0 and GW+C), to disentangle the complex set of experimentally observed satellite features attributed to the generation of plasmons and interband transitions. This combined experiment-theory strategy is able to uncover previously undocumented satellite features, improving our understanding of their direct relationship to tungsten's electronic structure. Furthermore, it lays the groundwork for future studies into tungsten-based mixed-metal systems and holds promise for the reassessment of the photoelectron spectra of other transition and post-transition metals, where similar questions regarding satellite features remain.
Offi F, Yamauchi K, Picozzi S, et al., 2021, Identification of hidden orbital contributions in the La<sub>0.65</sub>Sr<sub>0.35</sub>MnO<sub>3</sub> valence band, PHYSICAL REVIEW MATERIALS, Vol: 5, ISSN: 2475-9953
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- Citations: 2
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